Tube bending machine



Sept. 14, 1965 Filed Dec. 18, 1961 6 Sheets-Sheet 1 i g WI! w 5 00 w a N M I Q m Ill r-D- (D 1 I INVENTOR HENRY W. ROESSLER, JR.

ATTORNEY Sept. 14, 1965 H. w. ROESSLER, JR

TUBE BENDING MACHINE 6 Sheets-Sheet 2 Filed Dec. 18, 1961 INVENTOR HENRY w. ROESSLER, JR. BY +/%-%i/.

ATTORNEY p 1965 H. w. ROESSLER, JR

TUBE BENDING MACHINE 6 Sheets-Sheet 3 Filed Dec. 18, 1961 INVENTOR HENRY W. ROESSLER, JR.

ATTORNEY Se t. 14, 1965 H. w. ROESSLER, JR 3,205,690 TUBE BENDING MACHINE Filed Dec. 18, 1961 6 Sheets-Sheet 4 m N Lu m m m N) :5 m 2 IIIIHIHH FIE EI INVENTOR HENRY W. ROESSLER, JR.

BY aw 197W ATTORNEY p 14, 1965 H. w. ROESSLER, JR 3,205,690

TUBE BENDING MACHINE Filed Dec. 18, 1961 6 Sheets-Sheet 5 INVENTOR BY W4 ATTORNEY HENRY W. ROESSLER, JR.

United States Patent 3,205,690 TUBE BENDING MACHINE Henry W. Roessler, Jr., Pomona, Calif., assignor, by mesne assignments, to FMC Corporation, San Jose, Calif., a corporation of Delaware Filed Dec. 18, 1961, Ser. No. 160,094- 11 Claims. (Cl. 72150) This invention relates to tube bending machines and particularly to heavy duty machines capable of bending strong, relatively thick walled tubing.

Machines of the type to which this invention relates usually include a pair of die halves or die blocks, to be referred to as dies, having die faces or cavities for receiving tubing to be bent. After the straight tubing is placed between the dies and the dies are closed, a mandrel is inserted in the bore of the tubing, whereupon the dies are rotated through a predetermined angle to impart the bend to the tubing. Machines of this type present few problems in connection with the bending of ordinary copper or steel thin walled tubing, but such machines do not lend themselves to the bending of relatively strong, thick walled, tubing, including tubing made of intractable metal such as stainless steel. One of the problems presented by prior machines when employed for heavy duty service is that the dies tend to spring or separate under the heavy loads encountered, so that the tubing is not accurately maintained in position in the dies during bending. This results in a distorted product, and is due .to the fact that the mounting for the dies of prior machines has not been sufficiently rigid for heavy duty work.

An object of the present invention is to provide precisely cont-rolled bending of relatively thick-walled, or strong tubing.

Another object is to provide a mounting for the die blocks that is capable of withstanding the severe loads that arise during such bending operations, with a minimum of spring or distortion.

Still another object is to provide a die assembly mounting wherein the dies are relatively easily maintained in their closed position against the die separa-tng forces that are generated during the bending operation.

Briefly, these objects are accomplished by providing a split die assembly which has a main die rotatably mounted in the frame and a movable die supported from the main die for axial movement and closed thereagainst by a hydraulic cylinder mounted on the main die. The plane of separation of the dies is perpendicular to their axis of rotation, which plane is horizontal in the form of the invention described. The main die is provided with an exceptionally rugged mounting in a heavy frame wherein the periphery of the die is cylindrical and forms a large, load supporting bearing. This eliminates cantilever mounting of the main die and transfers the heavy loads encountered during the operation directly to the frame.

Another object is that of preventing drawing action on the tubing during bending, while simultaneously relieving the dies of a substantial portion of the load generated during the operation. Briefly, this is accomplished by providing a hydraulically projectable tube-pushing sleeve that engages the outer or free end of the tube during the bending operation, that is, during the time that the dies are being rotated for bending. The sleeve pushes against the tube and the tube is backed up by the dies, so that the entire tube bending force need not be supplied by the means provided for rotating the dies.

Another object of the invention is to provide a strong, rigid mounting for the tube-pushing sleeve, as well as for the mandrel, so that these parts can withstand transverse forces that might be exerted during the bending of relatively thick-walled tubing. This is accomplished by ice mounting the tube-pushing sleeve so that it slides in a massive base portion of the frame, there being but a short portion of the sleeve projecting from the frame for engaging the tube. The mandrel extends through the tube-pushing sleeve and through the operating cylinder for the sleeve and extends to the piston of a hydraulic motor that is mounted on one end of the hydraulic motor for the tube-pushing sleeve. With this construction, the tube-pushing sleeve slides along the mandrel during the bending operation, and provides increasingly effective support for the mandrel. This construction also provides for hydraulic operation of the mandrel itself.

Another object of the invention is to provide a tube bending apparatus of the power-turned die and tube-end pushing type just described which provides flexibility and control of the balance between the die turning and tubeend pushing forces, to accommodate various conditions that arise when bending tubes of various thicknesses and materials. Briefly, in the present invention this is accomplished by a hydraulic system which can be adjusted to provide aforesaid desired balance between the die turning and tube-end pushing forces. A feature or" the system is the provision of a separate pump for the die turning cylinder and tube-pushing cylinders, along with valve arrangements that intercouple these elements to make possible the balancing of one force against the other.

The manner in which these and other objects and advantages are accomplished will be apparent from the following detailed description of the invention and accompanying drawings:

In the drawings:

FIG. 1 is a side elevation of the apparatus of the present invention.

FIG. 2 is a plan of the apparatus with parts broken away.

FIG. 3 is an end elevation of the apparatus with the upper or movable die in its raised position and with parts broken away.

FIG, 4 is a fragmentary plan with parts broken away, including the mandrel operating cylinder and the upper die, which do not appear.

FIG. 5 is a side elevation of the apparatus with parts broken away, including the mandrel cylinder and the cylinder for operating the upper die, which do not appear.

FIG. 6 is a horizontal section taken on lines 66 of FIG. 3 showing the upper die only.

FIG. 7 is a horizontal section taken on lines 7-7 of PEG. 3 showing the die cavity in the upper die.

FIG. 8 is a vertical section taken on line 88 of FIG. 4 showing the relation of the lower die cavity to the tube being bent, the upper die appearing in phantom.

FIG. 9 is an enlarged fragmentary plan, with parts in section, showing the lower die only during a phase of the operation wherein a piece of tubing has been bent through an angle of The upper die has been removed in this view.

FIG. 10 is a vertical section taken on lines 10-10 of FIG. 9, except that the upper die is in place in this view.

FIG. 11 is a schematic diagram of the hydraulic control system for the apparatus of the present invention.

General arrangement of the apparatus The working elements of the apparatus are mounted on a heavy, relatively flat longitudinally extending cast frame 10. The frame rotatably mounts the lower die D, the major portion of which is cylindrical and which rotates in a large diameter bore or cavity in the frame so that the cavity serves as a bearing for the body of the die. The lower die D has the usual die cavity formed therein, and a complementary die cavity is formed in a vertically movable upper die E. The upper die is actually mounted on the lower die and can be opened and closed by means of a vertically extending hydraulic cylinder F. The lower end of the cylinder F is supported on the lower. die by a set of rods on which the upper die slides. The piston rod of cylinder F is connected to the upper die.

In order to turn the dies, a horizontal draw cylinder C is mounted on one side of the frame. A strong coil die return spring S (FIG. 4) is mounted on the other side of the frame, and a chain is connected between the piston rod of the draw cylinder C and the spring S for turning the dies.

A mandrel M is arranged to be moved into the bore of the tubing being bent, and the mandrel is advanced and retracted by a hydraulic cylinder G (FIG. 1). The hydraulic cylinder G for the mandrel is mounted on the frame so as to be axially aligned with a hydraulic cylinder H which operates a tube-pushing sleeve P (FIG. 4), the shank ofthe mandrel extending through a bore in the pusher sleeve.

During the bending operation, pusher cylinder H and pusher sleeve P engage the end of the tube between the dies and provide the initial bending action. As the bending proceeds, means are provided to bring the draw cylinder C into operation to assist in completing the bend.

Construction and mounting of the lower die Referring to FIGS. 1-5, the heavy cast mono-block frame 10 is formed with a vertically extending cylindrical bore or cavity 12 for receiving the generally cylindrical platen or body,13 of the lower die D. In addition to the bearing area provided by the frame directly, combined thrust and rotary bearing means support and center the lower portion of the rotatable lower die D. This additional bearing is provided by a pillow block housing 14 (FIGS. 3 and having a flange 16 for bolting the housing to the frame. A rigid web 17 is welded to and extends across the interior of the housing. The body 13 of the lower die has a hub 18 projecting downwardly therefrom, and a stub shaft 19 projects downwardly from the hub. Stub shaft 19 is rotatably mounted in a pillow block bearing 21 bolted to the web 17 by means of bolts 22. An upper thrust collar 23 is provided between the hub 18 and the pillow block bearing 21, and a retaining collar 24, is fastened to the lower end of stub shaft 19. In order to provide for turning of the dies, a double sprocket 26 is keyed to the hub 18 of the lower die.

The die cavity in the lower die, for receiving the tubing to be bent, is formed by a raised portion 27 (FIGS. 3, 4, and 9) that projects upwardly from the body 13 of the lower die D. This upstanding portion is integral with the die body portion 13, and has an arcuate recessed edge of generally quarter-round cross-section which defines a work-receiving face or die cavity 28. The cavity has a quarter-round cross-section for about 90 around the axis of rotation of the die, and then opens into a portion of generally half-round cross-section. The lower die is also provided with a socket cavity 29 forming a shoulder 30 (FIG. 9) for engaging the end of an expanded head 30a of the tubingW tobe bent. In FIG. 4 the unbent length of tubing W is shown in place in the lower die, with the expanded head portion 30a of the tubing mounted in socket 29, and bearing against shoulder 30. The expanded end 30aof the tube is also confined by a shoulder 30b of the socket that faces shoulder 30.

Construction and mounting of the upper die As previously mentioned, the upper die E is movably mounted directly upon the lower die D. The upper die has a body portion 31 (FIG. 3) formed to provide a quarter-round work receiving face or die cavity 28a for receiving the tubing, and a socket 29a for receiving the head of the tubing if one is provided. The socket forms shoulders 30c and 30d (FIG. 7) for engaging the expanded head of the tubing. In order to slidably mount the upper die on the lower die, guide rods 32 extend through apertures 32a in the upper die. As seen in FIG. 3, the lower ends of guide rods 32 are threaded as at 33, and are screwed into threaded sockets formed in the lower die. In FIG. 3 part of the lower die has been broken away to show this construction. In order to locate the upper ends of rods 32, the upper ends of the rods are shouldered (FIG. 5) and mounted in a plate 34 and retained thereon by nuts 36. Precise registry between the upper and lower dies when the dies are closed is assured by means of dowels 37 which project downwardly from the body portion 31 of the upper die and enter dowel holes 38 formed in the lower die. These dowel holes are best seen in FIGS. 4 and 9.

In order to mount the hydraulic cylinder F for raising and lowering the upper die E, a block 41 is welded on the upper side of 'the plate 34, and the lower cylinder head 42 for the hydraulic cylinder F is bolted to the block 41 by means of studs 43. The piston rod 44 for the hydraulic cylinder F extends through aligned apertures in block 41 and plate 34, and as seen in FIG. 3 the lower end of the piston rod is threaded into the upper die as at 46, the upper die having been partially broken away in this view to show this mounting. The upper end of the piston rod 44 is connected to a piston 45 in the cylinder F.

The die turning means As mentioned above, the hydraulic draw cylinder C assists in turning the dies during the bending operation. The inner end of draw cylinder piston rod 47 is connected to a piston 47a in the draw cylinder C, as seen in dotted lines in FIG. 5. The piston rod 47 has threaded into its outer end an anchor member 48. A double chain 49 is pinned to the anchor member 48 as seen in FIG. 5, and a threaded sleeve 50 surrounds the draw cylinder piston rod 47 and is threaded into the frame. Sleeve 50 provides an adjustable stop for limiting the retract, or bending, stroke of the draw cylinder piston rod. The chain 49 passes around the sprocket 26, which sprocket projects through apertures 52 formed in the pillow block housing 14 (FIGS. 1, 3, and 5), so that the chain clears the housing. The other end of the chain is pinned to a clevis 53 (FIGS. 3 and 4) by means of a pin 54. The clevis 53 mounts a spring anchor member 56 (FIG. 4) which has an enlarged head that fits within the free end of the return spring S. In order to anchor the other end of the spring S to the frame, the spring is confined in an elongated tube 57 which has a flange 58 at one end bolted directly to the frame. A plate 59 is held against the outer end of the tube 57, and a spring anchor member 61 extends through the plate and can be adjustably mounted in the plate by means of lock nuts 62 threaded on the anchor member. Thus, it can be seen that upon retraction of the draw cylinder piston rod, the dies rotate clockwise as viewed in FIG. 2, stretching the spring S in the process.

The pusher sleeve and its mounting As seen in FIG. 1, the pusher sleeve cylinder H is bolted directly to the main frame. The cylinder H has been broken away in FIG. 4 to show the piston 67 fastened to piston rod 68. In order to connect the pusher sleeve P to the piston rod, the pusher sleeve is formed with a threaded shank 69 (FIG. 4) that is threaded into a socket formed in the outer end of the piston rod 68. To provide for mounting of the mandrel M, aligned bores 71 and 71a are formed in the pusher sleeve P and the piston rod 68, respectively. As seen in FIGS. 4 and 9, the free end of the pusher sleeve P is beveled at 72, on

' the inner side thereof. The outer half of the end of the The mandrel and its mounting The mandrel cylinder G is mounted on the frame in axial alignment with the pusher sleeve cylinder H. As seen in FIGS. 1 and 2, channels '76 project rearwardly from the frame at each side of the cylinder head '77 of the pusher sleeve cylinder H. An end plate 7% joins the rearward ends of channels 76 and the mandrel cylinder G is bolted to the end plate. As seen in FIGS. 1 and 2, the outer end of mandrel M is adjustably connected to the piston rod 80 for the mandrel cylinder G. The end of the mandrel M is threaded at 81 to screw into a socket in the end of piston rod 80. To adjust the position of the mandrel, flats 82 and 83 are provided on the mandrel to receive wrenches by means of which the mandrel is held from turning while the piston rod 80 is turned. A locknut 84 maintains the adjustment. The outer or free end of the mandrel M is formed with a nose 86 which is rounded longitudinally as seen in FIG. 9 and is rounded transversely as seen in FIG. 10. The nose is adapted to support the outer portion of the tube as it is bent by rotation of the dies, and hence drawn along the nose 86.

Description of the mechanical operation A brief description of the mechanical operation of the structure just described will now be presented. This will be followed by a combined description of the hydraulic control system and how it provides a sequence of steps necessary for operation in the machine.

It will be assumed that the upper die E is in its raised position and that the mandrel M and pusher sleeve P have been retracted. The piston rod 47 for the draw cylinder C will be in its advanced position, as seen in FIG. 4, and the dies will have been returned by spring S to the starting position. A straight length of tubing W is inserted in the lower die cavity and into the socket in the pusher sleeve, whereupon the actuating cylinder F for the upper die E is caused to lower the upper die E against the lower die D to firmly mount the tubing in the die cavities. The mandrel cylinder G is now operated to project the mandrel the proper distance into the tubing, as determined by the adjustment 81. The pusher sleeve cylinder H is now actuated to advance the pusher sleeve P so that the shoulder 74 of the socket 73 engages the free end of the tubing W. Force is exerted by the pusher sleeve against the end of the tubing causing an initial turning of the two dies and consequent bending of the tube. When the pressure within the pusher cylinder H reaches a predetermined value, the draw cylinder C, which heretofore has only been acting to take up slack in the chain 49, is supplied with a higher pressure so that a portion of the load required to further bend the tubing W is assumed by the draw cylinder C. The means by which this load dividing and proportioning action is effected will be described in connection with the explanation of the hydraulic circuit.

The aforesaid action continues until the bend in the tubing is completed, at which time the chain anchor member 48 strikes adjustable stop 50 (FIG. 5). It will be noted that the bending operation stretches the die return coil spring S, so that upon completion of the bending operation, spring S exerts a torque on the die block tending to return it to its initial position. FIG. 9 shows a completed 90 bend imparted to the tubing.

Upon completion of the bend, the mandrel is withdrawn from the work and the pusher sleeve is withdrawn immediately thereafter. The oil under pressure is thereupon directed to the upper die cylinder F to raise the upper die E for removal of the bent tubing. Also, the draw cylinder C is disconnected from the high pressure source so that the return spring S can return the dies to their initial position, ready for a new operation.

The hydraulic system and its operation Since the various elements going to make up the 11ydraulic system are standard units these elements will not be described in detail, nor will the entire hydraulic circuit be traced independently of the description of its operation. The circuit has three control positions, Off, Forward, and Reverse, and as operation of the circuits represented by eachof these three control positions is described, the various elements in the circuits will be introduced and their function will be explained.

Ofi position-Referring to FIG. 11, which is a schematic diagram of the hydraulic system of the present invention, a push button panel 90 is provided which mounts the forward, reverse and oh push buttons. An electric supply line 99a for the valve control circuits leads to the push button panel 90 and this line is deenergized when the Off push button is depressed. An electric motor 91 is provided for driving the pumps and is mounted directly on an oil reservoir 92. The motor is normally running and drives a draw cylinder pump 93 and a pump 94 that operates the upper die, mandrel, and pusher cylinders. A hydraulic line from pump 93 leads to the center inlet connection of a solenoid operated fourway valve V, for controlling operation of the draw cylinder. The valve spool position is controlled by a low pressure solenoid 106 and a high pressure solenoid 113. When the off push button at panel 90 is in the Off position, both solenoids 106 and 113 are de-energized and the spool in valve V is centered. When the valve spool is centered, the valve directs fluid from the pump 93 out of the valve discharge line directly to a back pressure check valve 96, that is set to open at p.s.i., which diverts the oil back to the oil reservoir 92, as indicated by the dashed arrow. With this setting, pressure is instantly available for operation of the apparatus when the valve spool of valve V is shifted overcenter in either direction. Thus, with the push button control in the Oh? position, pump 93 is merely circulating oil at 65 p.s.i.

At the same time, pump 94 directs oil to a high pressure relief valve 97 and on to the inlet of a solenoid operated four-way spool valve X. The valve spool position is controlled by a forward solenoid 100 and reverse solenoid I116. The spool of this valve is also centered when the push button is in the 01f position and the valve redirects oil back to the reservoir by way of a back pressure check valve d8, set to open at 65 p.s.i., as indicated by the dashed arrow. Thus, when the push button is in the Off position, fluid is circulating under pressure in the supply lines of both pumps 93 and 94 to the valves V and X, and back to the reservoir, ready for instant operation.

Forward p0sitiolt.When the forward button is pressed at panel 90, electric supply line a is connected to an electric line 99 which energizes the forward solenoid 100 of the four-way valve X, and shifts the spool of that valve to direct fluid under pressure to a forward hydraulic line 101, as indicated by the solid arrows. Oil under pressure now flows to the upper side of the piston 45 in the upper die actuating cylinder F, to bring the upper die forcibly against the lower die, closing the die upon the tubmg W, which will have previously been inserted in the lower die cavity. The upper die is prevented from drifting toward the lower die by a counterbalance valve to be described presently.

A branch 191a of forward hydraulic line ltll directs fluid under pressure to a combined sequence and check valve 102. The term combined sequence and check valve, as it is used in this specification, refers to a conventional type valve unit that acts as a check valve in one direction and permits fluid flow in the other direction. When fluid pressure is applied to the valve in the direction in which it acts as a check valve, the valve remains seated until a predetermined pressure is attained, whereupon the valve opens and fluid flows through the valve.

When the piston in die cylinder F reaches the end of its stroke, pressure in branch line 101a builds up to a value sufficient to unseat the sequence valve 102, which now directs fluid under pressure to a branch hydraulic line 101b and on to the left side of mandrel cylinder Thus the mandrel is advanced to the proper posrtlon 1n ii fii a iicyi 1010 of forward hydraulic line 101 directs fluid under pressure to a second sequence and check valve 103, and after the piston of mandrel cyl nder G reaches the end of its stroke, pressure in branch line 101c builds up to a value sufficient to unseat the sequence valve 103, which now directs fluid to the left side of pusher cylinder H through a branch line 101d. This causes the pusher P to advance against the end of the tubing and start turning the dies.

Returning to the operation of the system, when the forward button is depressed, in addition to energiz ng the forward solenoid 100 of four-way valve X through electric line 99, depression of the forward button also energizes a branch electric line 104, leading to the low pressure solenoid 106 in the four-way cylinder valve V. Solenoid 106 is connected in series with a set of internal, normally closed pressure operated contacts 107 contained, in an adjustable pressure responsive switch Y. The pressure responsive element in switch Y is connected to the forward hydraulic branch line 101d by means of a branch line 101 The switch contacts 107 are closed when the fluid pressure in branch hydraulic line 101e is lower than the fluid pressure adjustment setting of the switch.

At the beginning of the action of the pusher cylinder H against the end of the tubing, the pressure developed in the pusher cylinder will be below that for which the pressure switch Y is adjusted, so that the circuit of solenoid 106 will be completed by the normally closed pressure switch contacts 107. Since electric line 104 was energized by depression of the forward button, the low pressure solenoid 106 in valve V will 'also have been energized upon depression of the forward button. This shifts the spool of valve V to the right, directing fluid from the pump 93 to a low pressure relief valve 108, which is set to deliver oil at a relatively low pressure, of -10 p.s.i.

Solid arrows indicate this flow. Oil at this pressure passes through a low pressure check valve 109 to a line 109a that is connected to a line 110 leading to an adjustable flow control valve 111. Oil from the flow control valve 111 passes into the right, or-retract side of the draw cylinder C. The pressure at which oil is delivered by low pressure relief valve 108 need only be high enough .to keep the chain 49 taut during the initial phase of operation. The flow control valve 111 acts to control oil flow during the stage of high pressure operation, as will be explained presently, and serves no purpose during the initial, low pressure stage of operation now being described.

As mentioned, the application of oil under low pressure to the left side of pusher cylinder H, when the forward button was pressed, advances the pusher sleeve P against the end of the work, and causes the dies to turn, initiating bending action. The bending is done by the pusher sleeve and the pressure in the draw cylinder C is only sufficient to take up the slack in the chain. Means are provided to automatically cause the draw cylinder to assist in the bending action at a predetermined time in the cycle. As bending continues, resistance to the turning of the dies increases, and the pressure in the pusher cylinder H, that operates pusher P, rises. This rise in pressure is sensed by the pressure switch Y, because the switch is connected into branch line 101d that leads to the left or advance side of pusher cylinder H. A point in the cycle is soon reached wherein the pressure applied to pressure switch Y rises to equal that for which the switch is set, whereupon the electric switches in pressure switch Y are hydraulically operated. The pressure setting of switch Y will ordinarily range from 500 to 1,000 psi. Hy-

draulic operation of the switch Y opens the normally closed contacts 107 in the electric line 104, which contacts are Wired in series with the low pressure solenoid 106 of the four-way valve V. Simultaneously, hydraulic operation of the switch Y closes a set of normally open internal contacts 112 in an electric line 112a connected to an external electric supply line and to the high pressure solenoid 13 in valve V. Thus, when pressure in the pusher cylinder and pressure switch Y reaches the pre-set value, the high pressure solenoid 113 is energized by the increased pusher cylinder pressure. Since the low pressure solenoid 106 has been de energized by the same action, energization of the high pressure solenoid 113 causes the spool of valve V to shift to the left. As indicated by the dot-dash arrows, this directs fluid from the pump 93 through a high pressure relief valve 114, to line 110, and hence to the adjustable flow control valve 111. The high pressure relief valve 114 passes oil on to line until the pressure rises to a pre-set value which will be somewhat higher than the setting for pressure switch Y. If that pressure is exceeded, the high pressure relief valve 114 opens the pressure line to an exhaust line 114a.

Returning to a description of normal operation, the right, or retraction side of the draw cylinder C, now receives fluid at an operating pressure limited only by the setting of the high pressure relief valve 114. The force exerted on the chain 49 by retraction of the draw cylinder piston now does more than take up the slack in the chain. The force is now such as to assist in turning the dies for completing the bending of the tubing W. Thus, before the cycle is completed, the work of turning the dies and bending the tubing is apportioned between the pusher cylinder H and the draw cylinder C.

The interaction of the pusher and draw cylinders and the act-ion of flow control valve 111 in completing the bend, may be explained as follows: If the resistance to bending, and hence to rotation of the dies, is not too high, the bending operation will proceed at a certain rate. The flow control valve 111 resists oil flow through the valve in proportion to the rate of flow, and hence the valve limits the rate at which the draw cylindercan retract. Thus, the flow control valve 111 controls the contribution of the draw cylinder to the bending operation. If bending resistance increases, the rate of die rotation decreases, the throttling effect of the flow control valve 111 decreases, and there is a greater pressure built up in the draw cylinder. Thus, the contribution of the draw cylinder to the bending operation is increased.

Adjustment of the pressure setting of the pressure switch Y, and of the flow control valve 111, can be made to balance these forces so that very little load is applied to the bearings mounting the lower die D in the frame. These adjustments are facilitated by gauges 111a and 111b in the pressure lines to the draw and pusher cylinders, respectively. These forces need not be adjusted so as to perfectly balance, the adjustment of pressure switch Y and flow control valve 111 can be such as to distribute the working forces between the pusher sleeve P and the draw cylinder C in any manner found to bend the tubing and relieve strain upon the parts with a minimum of drawing of the tubing.

It will be noted that the pusher cylinder H and the draw cylinder C are of substantially the same diameter, but that the draw cylinder C operates on a larger radius arm and hence has a superior mechanical turning advantage. However, tendency of the draw cylinder C to pull the end of the work away from the pusher sleeve can 'be-overcome by adjustment of the flow control valve 111 which restricts the rate of flow of oil to the draw cylinder. Of course, the diameters of the two cylinders need not be the same.

When the right hand side of the draw cylinder C is receiving fluid under high operating pressure, high pressure oil is prevented from returning to the sump by way of line 10% by the low pressure check valve 109.

Reverse psiti0n.-After completion of the bend in the tubing, the reverse button in the panel 90 will be pressed. This mechanically releases the forward button, which in turn de-energizes electric line 99 and hence deenergizes the forward solenoid 100 in four-way valve X. Release of the forward button also opens the electric line 104 connected to the low pressure solenoid 106 in valve V, so that even though pressure in pressure switch Y falls and normally closed contacts 107 in the switch re-close, low pressure solenoid 106 will remain de-energized.

The reverse button itself energizes an electric line 115 connected to the reverse solenoid 116 in four-way valve X, which shifts the spool in that valve to direct oil under pressure to a reverse hydraulic line 117. As indicated by the dotted arrows, line 117 leads directly to the right, or retract side of the mandrel cylinder, causing withdrawal of the mandrel M. A branch 117:: of the reverse line 117 leads to a combined sequence and check valve 118. When the piston in the mandrel cylinder G reaches the end of its retract stroke, pressure in branch line 117a builds up to a value sufficient to unseat sequence valve 118, which now directs fluid through a branch line 117b leading to the right, or retract side of the pusher cylinder H. The pusher sleeve P is now withdrawn. When the piston in the pusher cylinder H reaches the end of its retract stroke, pressure in branch reverse line 1171) builds up to a value sufiicient to unseat a combined sequence and check valve 121 mounted in a line 1170 that branches from line 117b. Sequence valve 121 now directs oil to an adjustable counterbalance check valve 122, which, in turn, directs fluid to the lower or retract side of the upper die operating cylinder F. This lifts the upper die block E, so that the completed part can be removed, the pusher P and the mandrel M having been withdrawn. When the upper die cylinder piston reaches the end of its stroke, and since all of the other pistons are at the end of their strokes, hydraulic pressure in the reverse hydraulic line 117 and in the line from pump 94 to valve X builds up and cracks the high pressure relief valve 97, diverting the fluid from pump 94 back to the reservoir, although this condition is ended when the off button is pressed and valve X is again centered.

The counterbalance check valve 122 is provided to prevent the upper die block E from slowly drifting downward between cycles of operation, when the off button is pressed. This is necessary because when the off button is pressed, the spool of four-way valve X will center and hence could not prevent fluid from flowing from the lower side of the upper die actuating cylinder F back through sequence valves 121 and 118, reverse line 117, back through the four-way valve X, and on to the reservoir. The pressure setting of counterbalance check valve 122 is high enough to provide this holding function but not too high to hold the cylinder piston back against pressure in the forward line 101. The counterbalance valve 122 thus partially regulates motion of the upper die E toward lower die D as the dies are closed.

As a result of pressing the reverse button, the mandrel and pusher sleeve have now been withdrawn and the upper die E has been raised to clear the work. The dies can be returned to the starting position, if pressure in line 110 leading to the draw cylinder is relieved so that the piston in the draw cylinder is permitted to advance to the right under force of the spring S. Such is the case, and this operation takes place as follows: Since pressing the reverse button energized the reverse solenoid 116 in four-way valve X and shifted the valve to direct fluid to the reverse hydraulic line 117, fluid under pressure is no longer directed by the four-way valve X to the forward line 101, rather, the forward line 101 is connected to exhaust by the four-way valve X. When this occurs, the various branches of line 101 are no longer pressurized, so that the pressure switch Y, which is responsive to pressure in branch line 101e, is now substantially relieved of pressure. The pressure switch Y now shifts to its initial or normal position. In this position, branch line 112a of the electric supply line is opened by the normally open contacts 112 in the pressure switch Y, thereby deenergizing the high pressure solenoid 113 in the four-way valve V associated with the draw cylinder. It will be recalled that when the reverse button was depressed, the low pressure solenoid 106 in four-way valve V associated with the draw cylinder was also deenergized, because of the mechanical interlock between the reverse button and the forward butt-on. Since both solenoids 106 and 113 in four-way valve V are now de-energized, the spool of valve V will center, and oil from the pump 93 will be directed by valve V through the back pressure check valve 96, and back to the reservoir. When this occurs, a fluid path is also established from the right or retract side of the draw cylinder C to the reservoir. This path is from the draw cylinder, through a low pressure check valve 119 set to open at a low pressure such as 5 p.s.i., back through the high pressure relief valve 114, through the centered four-way valve V, through the back pressure check valve 96, and on to the reservoir. When the pressure is thus relieved in the right or retract side of draw cylinder C, the spring S can turn the dies, advancing the piston 47a in the draw cylinder to the right, and bringing the dies to their initial position. The completed bent tube can now be removed from the lower die.

The off button can now be pushed and the machine will be ready for insertion of a new work piece and another cycle of operation. As previously described, pushing the off button centers the spools of both fourway valves. Fluid from pump 93 passes through fourway valve V and back pressure check valve 96 at 65 p.s.i., and hence back to the reservoir. Fluid from pump 94 passes through high pressure relief valve 97, four-way valve X and back pressure check valve 98 at 65 p.s.i., and hence back to the reservoir. The upper die will remain in its retracted position because of the checking action of counterbalance check valve 122, previously described.

Synopsis of the operation of the hydraulic system 0 5" p0sition.The four-way valves V and X are centered, and oil is circulating at 65 p.s.i. through back pressure check valves and back to sump, ready for operation. The upper die is hydraulically retained in its raised position by the counterbalance check valve 122. The pusher sleeve and the mandrel are retracted. The spring S is holding the lower die in its starting position. The tubing W can be inserted in the lower die.

Forward position-first stage.The four-way valve X directs oil to forward hydraulic line 101. The upper die closes, and the mandrel M advances and stops. The pusher P advances, engages the work, and starts the bending of the work. The four-way valve V is shifted to direct oil to the draw cylinder C through L.P. relief and check valves and the flow control valve 111 to take up slack in chain. At low pressure, the flow control va ve has no effect, and the pressure switch Y is not activated.

"F0rward p0siti0n-sec0nd stage.The resistance to bending increases, and pressure in the forward hydraulic line 101 increases correspondingly. The pressure switch Y is activated. The four-way valve V now directs oil through the HF. relief 114 and flow control valve 111 to the draw cylinder C so that the latter now assists in the bending action. The degree of assist is determined by adjustment of flow control valve 111 and the pressure switch Y. The bending is completed as the pusher continues to press against work and the draw cylinder retracts to turn dies by means of the chain, until chain block 48 strikes adjustable stop.

Reverse p0sition.-The four-way valve X is shifted to supply high pressure oil to the reverse hydraulic line. The forward hydraulic line is connected to exhaust through the four-way valve. The mandrel is retracted.

Then the pusher sleeve is retracted, and the upper die is raised. The low pressure solenoid of four-way valve V has already been de-energized by depression of reverse button which lifts forward button and opens low pressure solenoid circuit. The drops in pressure in the for- 'ward line 101 restores the pressure switch Y to normal condition. The high pressure solenoid in four-way valve V is de-energized by the normally open contacts in pressure switch Y, and the four-way valve V centers and connects draw cylinder to sump. The spring S turns the dies to the starting position.

Having completed a detailed description of the invention, it can be seen that the apparatus is particularly adapted for heavy duty work and for bending'strong, thick walled tubing. The dies are rigidly mounted within the apparatus frame, and the movable die is mounted directly upon the lower die block, there being no cantilever action in the mounting. The work will not spread the dies apart during the bending operation, and the bearing for the lower die need not assume the die clamping force. The mandrel is supported by the pusher sleeve and this support is maintained and even improved as the work proceeds, by the advance of the pusher sleeve over the mandrel. The pusher sleeve itself is supported close to the work, so that both of these elements are rigidly mounted'and maintain their alignment in operation.

Because of this simple and rugged design and construction of the bending machine of the invention, strong heavy duty tubing is readily bent without undue straining of the machine and without springing of the parts. For example, 3' OD. tubing, having a wall thickness of /2 inch or over, can readily be bent to a 3%" center line radius with the present machine, it only being necessary to provide a pusher sleeve and a draw cylinder of ade quate size, and a motor and pump set of suitable capacity.

The machine of the invention is capable of cold-bending heavy duty steel tubing, including tubing that has been cold drawn or forged and hence has had imparted thereto a favorable grain distribution. Since cold working of steel parts. gives improved grain distribution and increases the yield point of the part, use of the machine of the invention to further cold work parts results in a strong product that will withstand high pressures. In

' fact, in some cases the ability of the machine to impart a cold bending operation, including a cold bending operation performed on a part that was previously cold worked and has not been reheated, often makes it possible to employ a grade of steel for the part that is somewhat cheaper than the grade that would otherwise be necessary. This is not to imply that the machine cannot be employed to bend heated parts, if desired.

The hydraulic system provides for precise and flexible control and relative adjustment of the forces exerted by the pusher sleeve and draw cylinder respectively, so that these forces can be balanced. or accommodated to the work at hand to produce the best job with a minimum of strain of the apparatus. This action is facilitated by the pressure switch and flow control valve in the hydraulic system coupled with the fact that the pump and hydraulic circuits for the draw cylinder are independent of the pump and hydraulic circuits for the pusher cylinder. All of these features cooperate and combine to produce a rugged, heavy duty bending machine, having a long life under severe operating conditions, and capable of adjustment and control for optimum handling of various types of work encountered. Yet the machine itself is essentially very simple and has relatively few parts.

The invention having thus been described, that which is claimed to be new and which is desired to be protected by Letters Patent is:

1. A tube bending machine comprising a frame, a relatively large diameter cylindrical bearing cavity formed in said frame, a first die having a cylindrical body portion rotatably mounted in, and engaging the wall of said bearing cavity, an upstanding die portion integral with said body portion of said first die and having formed therein a first die cavity, means for maintaining the cylindrical body portion of said first die in the bearing cavity of the frame during rotation of the die for bending, a second die having a body portion and a die portion having formed therein a second die cavity, means for mounting said second die directly on said first die for simultaneous rotation of both dies, and for opening and closing motion of said second die while the first die remains in the body cavity of the frame, means for opening and closing said second die, a mandrel mounted in said frame for motion tangential of said die cavity, and means for rotating said first die while it is maintained in said bearing cavity for bending a length of tubing gripped between said dies, when the second die is closed.

2. A tube bending machine comprising a frame, a

relatively large diameter cylindrical bearing cavity formed in said frame, a first die having a cylindrical body portion rotatably mounted in said frame bearing cavity, a plurality of guide rods projecting axially from said first die, a second die slidably mounted on said rods for opening and closing motion relative to said first die, a hydraulic cylinder mounted on the ends of said rods for opening and closing said secondv die, means on said dies that cooperate to form a tube-receiving .die cavity, a mandrel mounted in said frame for motion tangential of said die cavity, and means rotating said first die in said bearing cavity for bending a length of tubing gripped between said dies.

3. A t-ube bending lmaohine comprising a frame, a split die block assembly rotatably mounted on said frame and having a tube-receiving cavity, a tube pushing sleeve slidably mounted in said frame, a hydraulic cylinder for advancing said sleeve against the tube to rotate said die assembly in a direction to bend the tube, a hydraulic cylinder on said frame for turning said die assembly to assist in bending the tube, a first pump for supplying fluid under pressure to said hydraulic sleeve-advancing cylinder, a second pump for supplying fluid under pressure to said die assembly cylinder, valve means between said second pump and die assembly cylinder, and means responsive to the build up of pressure in said sleeve-advancing cylinder for operating said valve means to supply fluid under pressure to said die assembly cylinder.

4. A tube bending machine comprising a frame, a relatively large diameter cylindrical bearing cavity formed in said frame, a first die having a cylindrical body portion rotatably mounted in said bearing cavity, a second die mounted on said first die for opening and closing motion relative thereto, means for opening and closing said sec- 7 0nd die,-rmeans on said dies that cooperate to form a tubereceiving die cavity, a tube pusher sleeve slidably mounted in said frame for engaging the end ofa tube gripped :between said dies, a hydraulic cylinder on said frame for advancing said tube pusher sleeve, a mandrel slidably mounted in said sleeve, a hydraulic die-turning cylinder mounted on said frame, and means connecting said latter cylinder to said first die for rotating said dies.

'5. A tube bending machine comprising a frame, a relatively large diameter cylindrical bearing cavity formed in said frame, a first die having a cylindrical body portion rotatably mounted in said bearing cavity, a second die mounted on said first die for opening and closing motion relative thereto, means for opening and closing said second die, means on said dies that cooperate to form a tube-receiving die cavity, a tube pusher sleeve slidably mounted in said frame for engaging the end of a tube gripped between said dies, a hydraulic cylinder on said frame for advancing said pusher sleeve, a mandrel slidably mounted in said sleeve, a hydraulic draw cylinder mounted on said frame, a sprocket on said first die, a tension spring on said frame, and a chain passing around said sprocket and connected to the piston rod of said draw cylinder and to said spring for rotating said dies.

6. A tube bending machine comprising a frame, a split die assembly rotatably mounted in said frame, a tube pusher sleeve slidably mounted in said frame for engaging the end of a tube gripped between said dies, a hydraulic sleeve pusher cylinder on said frame for advancing said sleeve, a mandrel slidably mounted in said sleeve, a hydraulic draw cylinder mounted on said frame, a sprocket on said first die block, a tension spring on said frame, a chain passing around said sprocket and connected to the piston rod of said draw cylinder and to said spring for rotating said dies.

7. A tube bending machine comprising a frame, a split die assembly rotatably mounted in said frame, a tube pusher sleeve slidably mounted in said frame for engaging the end of a tube gripped between said dies, a hydraulic sleeve pusher cylinder on said frame for advancing said sleeve, a mandrel slidably mounted in said sleeve, a hydraulic mandrel operating cylinder mounted on said frame in axial alignment with said sleeve pushing cylinder, a hydraulic die-turning cylinder mounted on said frame, and means connecting said latter cylinder to said die assembly for rotating said die assembly.

8. A tube bending machine comprising a frame, a split die assembly rotatably mounted on said frame and having a tube receiving cavity, a tube pusher sleeve slidably mounted in said frame, a hydraulic cylinder for advancing said sleeve against the tube to rotate said die assembly in a direction to bend the tube, a hydraulic draw cylinder on said frame for turning said die assembly to assist in bending the tube, a first pump for supplying fluid under pressure to said hydraulic sleeve-advancing cylinder, a second pump for supplying fluid under pressure to said die turning cylinder, valve means between said second pump and said die turning cylinder, means responsive to the build up of pressure in said sleeve advancing cylinder for operating said valve means to supply fluid under pressure to said die turning cylinder, and an adjustable flow control valve between said valve means and said die turning cylinder.

9. A tube bending machine comprising a frame, a relatively large diameter cylindrical bearing cavity formed in said frame, a first die having a cylindrical body portion rotatably mounted in said bearing cavity, a second die adjustably mounted on said first die, a tube pushing sleeve slidably mounted in said frame, a hydraulic cylinder for advancing said sleeve against the tube to rotate said dies in a direction to bend the tube, a hydraulic draw cylinder on said frame for turning said dies to assist in bending the tube, a first pump for supplying fluid under pressure to said hydraulic sleeve-advancing cylinder, a second pump for supplying fluid under pressure to said die turning cylinder, valve means between said second pump and die turning cylinder, means responsive to the build up of pressure in said sleeve-advancing cylinder for operating said valve means for supplying fluid under pressure to said die turning cylinder, and an adjustable flow 14 control valve between said valve means and said die turning cylinder.

10. A tube bending machine comprising a frame, a relatively large diameter cylindrical bearing cavity formed in said frame, a first die having a cylindrical body portion rotatably mounted in said bearing cavity, a second die adjustably mounted on said first die, a tube pushing sleeve slidably mounted in said frame, a hydraulic cylinder for advancing said sleeve against the tube to rotate said dies in a direction to bend the tube, a sprocket on said first die, a hydraulic draw cylinder on one side of said frame, a spring on the other side of said frame, a chain passing around said sprocket and connected to said draw cylinder and to said spring for turning said dies to assist in bending the tube, a first pump for supplying fluid under pressure to said hydraulic sleeve-advancing cylinder, a second pump for supplying fluid under pressure to said draw cylinder, valve means between said second pump and draw cylinder, means responsive to the build up of pressure in said sleeve-advancing cylinder for operating said valve means to supply fluid under pressure to said draw cylinder, and an adjustable flow control valve between said valve means and said draw cylinder for regulating the force exerted by said draw cylinder on said dies relative to the force exerted thereon by said sleeve-advancing cylinder.

11. A tube bending machine comprising a frame, a split die assembly rotatably mounted in said frame, a tube pushing sleeve slidably mounted in said frame, a hydraulic cylinder for advancing said sleeve against the tube to rotate said die assembly in a direction to bend the tube, a sprocket on said die assembly, a hydraulic draw cylinder on one side of said frame, a spring on the other side of said frame, a chain passing around said sprocket and connected to said draw cylinder and spring for turning said die assembly to assist in bending the tube, a first pump for supplying fluid under pressure to said hydraulic sleeve-advancing cylinder, second pump for supplying fluid under pressure to said draw cylinder, valve means between said second pump and said draw cylinder, means responsive to the build up of pressure in said sleeve-advancing cylinder for operating said valve means to supply fluid under pressure to said draw cylinder, and an adjustable flow control valve between said valve means and said draw cylinder for regulating the force exerted by said draw cylinder on said die assembly relative to the force exerted thereon by said sleeve-advancing cylinder.

References Cited by the Examiner UNITED STATES PATENTS 1,135,875 4/15 Brinkman 153-40 2,814,327 11/57 Charlton 15340 2,856,981 10/58 Hitz 153-48 3,016,943 1/62 Kilham 15340 CHARLES W. LANHAM, Primary Examiner.

WILLIAM J. STEPHENSON, Examiner. 

1. A TUBE BENDING MACHINE COMPRISING A FRAME, A RELATIVELY LARGE DIAMETER CYLINDRICAL BEARING CAVITY FORMED IN SAID FRAME, A FIRST DIE HAVING A CYLINDRICAL BODY PORTION ROTATABLY MOUNTED IN, AND ENGAGING THE WALL OF SAID BEARING CAVITY, AN UPSTANDING DIE PORTION INTEGRAL WITH SAID BODY PORTION OF SAID FIRST DIE AND HAVING FORMED THEREIN A FIRST DIE CAVITY, MEANS FOR MAINTAINING THE CYLINDRICAL BODY PORTION OF SAID FIRST DIE IN THE BEARING CAVITY OF THE FRAME DURING ROTATING OF THE DIE FOR BENDING, A SECOND DIE HAVING A BODY PORTION AND A DIE PORTION HAVING FORMED THEREIN A SECOND DIE CAVITY, MEANS FOR MOUNTING SAID SECOND DIE DIRECTLY ON SAID FIRST DIE FOR SIMULTANEOUS ROTATION OF BOTH DIES, AND FOR OPENING AND CLOSING MOTION OF SAID SECOND DIE WHILE TGHE FIRST DIE REMAINS IN THE BODY CAVITY OF THE FRAME, MEANS FOR OPENING AND CLOSING SAID SECOND DIE, A MANDREL MOUNTED IN SAID FRAME FOR MOTION TANGENTIAL OF SAID DIE CAVITY, AND MEANS FOR ROTATING SAID FIRST DIE WHILE IT IS MAINTAINED IN SAID BEARING CAVITY FOR BENDING A LENGTH OF TUBING GRIPPED BETWEEN SAID DIES, WHEN THE SECOND DIE IS CLOSED. 